Letters and blogs

A longer perspective

Jack Schofield (Technophile, 20 August) credits Professor Charles Wheatstone with "working out how images from two eyes create a sense of depth" in 1838. Sir Charles was certainly one smart dude but Euclid and Galen in antiquity understood the principal of binocular vision. Jacopo Chimenti in the 16th century produced drawings made from a slightly different angle to be viewed as stereoscopes. Wheatstone was just repeating the trick in 1838.

Professor Brian Winston, Lincoln Professor of Communications, University of Lincoln

• Jack is wrong to say that the Victorian craze for 3D didn't survive the Kodak box camera. 3D photography has had regular resurgences every 30 years or so since the 1850s. Even between these peaks, camera companies, including Kodak, made extensive stereo ranges. I'd agree that the 1980s comeback with the Nimslo was a bit of a damp squib, but 30 years on we're ready, yet again, for stereo photography to come back … Here's looking beyond to 2040.

Michael Pritchard, Watford

In defence of Wikipedia

Root Cartwright (Letters, 20 August) misses a key point about Wikipedia; it's a secondary source. A good Wikipedia entry will contain a host of links to primary sources of info, along with cross-references to related Wikipedia pages if you want to drill down a bit further. When the links don't do it for you, the text will usually provide clues to search terms that are useful. Wikipedia has a clear policy that it does not publish original research and that articles must cite sources. Articles that don't cite primary sources have notes inserted in them by the über-editors requesting citations.

If, as Root suggests, we should think of the internet itself as the "encyclopedia", then Wikipedia should be seen as the best attempt so far at a front-end. Google just doesn't hack it in that role. Want an example? Search on a mainstream A-level topic such as "Cartesian dualism". Google's first page from 286,000 returns is interesting, but compare and contrast the Wikipedia entry. Here is an excellent start for that bit of coursework; it's easy to monitor for plagiarism; and there's a clear statement about why the article was downgraded in July this year from "Good" to "B-class" status.

David Hopson, West Wittering

Doubts on free ebooks

I had an interesting discussion the other day with several friends. The question that I posed was, "at what point have you invested so much time into reading a novel that you will finish it no matter what?" The context for the question is that, as a publisher, I want to allow readers a good sampling of a book before they commit to buying it. A chapter? Several chapters? Half the book? The other side of this equation is that once a reader has reached this point of no return – when you have to flip to the next page – it should be trivial to sell them the book. Cory Doctorow posted in the Guardian a couple of days ago that you should give the entire ebook away – and readers will come back for printed copies (Why free ebooks should be part of the plot, 20 August). This actually makes some sense if ebooks were to include commercials and other means for authors and publishers to make money. Otherwise, Stephen King's experiment with free, serialised giveaways proves this is not yet economically feasible.

Booksellers know that personal recommendations from friends are the best way to sell books. A publisher's marketing for a book is an excellent way to get it into some readers' hands, and the word of mouth enabled by freely copyable ebooks acts as a force-multiplier to expand the publisher's efforts.

I like both the work of Cory Doctorow and his theory that free eBooks help physical book sales. But try convincing an enormous multinational corporation that there's merit to that theory. While you're doing that, I'll be flapping my arms. Let's see if I can fly to the moon before you win them over.